Chitosan/Silica Hybrid Nanogels by Inverse Nanoemulsion for Encapsulating Hydrophilic Substances

Abstract

A strategy for the preparation of a hybrid chitosan/silica nanohydrogel is reported, which combines the gelation of chitosan in a nanoemulsion system with a sol–gel process to produce silica. Chitosan is used as a biopolymer matrix, while silica acts as a structuring additive. Hydrogel nanocapsules are obtained through the ionic interaction of the cationic groups of chitosan with the anionic groups of sodium triphosphate (STP), which is used as a physical cross‐linker. Two alternative preparation methods are compared in this work: in the first one, STP is added to the continuous phase of an inverse emulsion of chitosan; in the second one, the fusion of droplets of two emulsions containing separate chitosan and STP takes place. The size of the obtained nanocapsules ranges from 50 to 200 nm. The efficiency of the formed hydrogel for entrapping a hydrophilic model substance (erioglaucine disodium salt) is investigated for the two systems by studying the release in a neutral aqueous medium. The results indicate that the hydrophilic cargo is efficiently encapsulated by both preparation methods, although the droplet‐fusion method yields more stable suspensions. As a general observation, the release behavior of erioglaucine is systematically retarded when silica is present in the systems.